The present invention relates the message routing infrastructure of a signaling network. More particularly, the present invention relates to methods and systems for collapsing or reducing signal transfer point (STP) infrastructure requirements in a signaling network.
Conventional telecommunications networks include two distinct communication pathways or subnetworksxe2x80x94a voice network and a signaling network. These two networks function in a cooperative manner to set up and tear down calls between users. As implied by its name, the voice network handles the transmission of voice (or user data) information between users. The signaling network has a number of responsibilities, which include call setup, call teardown, and database access. In simple terms, the signaling network facilitates the dynamic linking together of a number of discrete voice-type communication circuits such that a voice-type connection is established between the calling and called party. Additionally, the signaling network provides a framework through which non-voice-related information may be transported, with this data and transport functionality being transparent to the users. This signaling technique is often referred to as out-of-band signaling, where the term xe2x80x9cbandxe2x80x9d implies voice band. The signaling protocol most commonly employed in communication networks around the world is the signaling system 7 (SS7) protocol.
From a hardware perspective, an SS7 network includes a plurality of SS7 nodes, generically referred to as signaling points (SPs), that are interconnected using signaling links, also referred to as SS7 links. At least three types of SPs are included in an SS7 network: service switching points (SSPs), signal transfer points (STPs) and service control points (SCPs). Within an SS7 signaling network, each SP is assigned an SS7 network address, which is referred to as a point code (PC).
An SSP is normally installed in Class 4 tandem or Class 5 end offices. The SSP is capable of handling both in-band signaling and SS7 signaling. An SSP can be a customer switch, an end office, an access tandem and/or a tandem. An STP routes signaling messages. STPs are usually installed as mated pairs for reliability purposes. Finally, SCPs control access to databases, such as 800 number translation databases, 800 number carrier identification databases, credit card verification databases, etc.
Signaling links are transmission lines used to connect SPs together. Conventional signaling links are dedicated bi-directional facilities operating at 56 kbps in the U.S. and Canada and at 64 kbps when clear channel capability is deployed. Normally, every link has a mate for redundancy and enhanced network integrity. It will be appreciated that in some cases, traditional 56 kbps dedicated SS7 signaling links may be replaced by high-speed, shared-bandwidth signaling links, such as IP or ATM signaling links.
FIG. 1 is a network diagram that depicts an exemplary SS7 network, generally indicated by reference numeral 100. As discussed above, STPs are typically deployed in a mated pair configuration for redundancy and reliability. However, for the purposes of illustration, only single STPs are shown in sample network 100. In FIG. 1 network 100 includes four separate networks 102, 104, 106, and 108. In the illustrated example, network 102 includes a pair of signaling points 118 and 120, network 104 includes a pair of signaling points 122 and 124, network 106 includes a pair of signaling points 126 and 128, and network 108 includes a pair of signaling points 130 and 132. STPs 110, 112 , 114, and 116 perform SS7 routing for networks 102, 104, 106, and 108, respectively. As indicated in FIG. 1, STP A 110 is assigned a true point code (TPC) of 1-1-1, STP B 112 is assigned a true point code of 2-2-2, STP C 114 is assigned a true point code of 3-3-3, and STP D 116 is assigned a true point code of 4-4-4.
The term xe2x80x9ctrue point codexe2x80x9d as used herein refers to the point code that an STP recognizes as its own for network management purposes. An STP terminates messages that are addressed to its true point code. A message addressed to the TPC of a particular STP would not be xe2x80x9cthrough switchedxe2x80x9d or routed by the receiving STP but would instead be terminated and processed by the STP. STPs also use a TPC when originating network management messages.
In an SS7 signaling network there are three categories of network management: traffic management, link management, and route management. Traffic management is the process of diverting messages away from failed links. Link management involves the activation and deactivation of signaling links. Route management is responsible for both re-routing messages around failed SS7 signaling points and controlling the flow of messages to any given signaling point in the network.
Those skilled in the art of SS7 signaling network operation will appreciate that such a network management strategy provides a layered approach to managing abnormal events in an SS7 network. The SS7 protocol provides procedures designed to minimize the effects of network congestion and outages from the link level all the way up to the route level. Within the SS7 message transfer part (MTP) protocol, level two of the protocol detects errors on individual signaling links.
When an error on a signaling link is detected, level two reports the error to level three, which in turn must determine the proper error resolution procedures to invoke. In general, SS7 error resolution procedures begin at the lowest level, the link level, and work their way up to the highest level, the route level. While these procedures do not have a direct impact on routing or the status of signaling points, they do, however, trigger other level-three network management events.
Traffic management is effected by link management primarily because traffic management must divert traffic away from a link that link management has failed and removed from service. In this manner, traffic management ensures the orderly delivery of all diverted traffic. When a link fails, traffic management transfers unacknowledged messages to another link buffer and subsequently retransmits these messages on a different, in-service signaling link. It should be noted that the traffic management process does not divert traffic away from a signaling point. The purpose of traffic management is simply to redirect traffic at a signaling point to a different signaling link. Traffic management does, however, impact routes and route-sets to specific destinations. If a particular route is used by another signaling point to reach a destination, and traffic management has diverted traffic away from that route, adjacent signaling points may have to invoke route management procedures.
At the highest level, route management diverts traffic away from signaling points that have become unavailable or congested. Regardless of the root cause, traffic management and link management will be involved at the affected signaling point. At the same time, all the signaling points around the affected signaling point are forced to invoke route management procedures to prevent messages from becoming lost.
In an SS7 network, the above-described network management functionality is accomplished through the use of specific network management messages. A sample structure of a typical SS7 network management message or message signaling unit (MSU) 150 is illustrated in FIG. 2. It will be appreciated by those skilled in the art of SS7 signaling communications that the signaling information field (SIF) 152 of MSU 150 includes data associated with a particular point code that is experiencing difficulty or a particular link that has failed. Additional status information, priority codes, and other relevant maintenance codes may also be included in SIF 152, depending upon the particular type of network management message being sent. A routing label field 154 may contain a number of additional fields, including a destination point code (DPC) field 156, an originating point code (OPC) field 158, and a concerned point code (CPC) field 160. Depending on the particular type of network management message, the information conveyed in these fields may enable an adjacent node to determine which other node in the network is experiencing difficulties and to which node in the network status queries should be directed. In most instances, a network management message originated by an STP in a signaling network will include an OPC value that is the true point code assigned to that STP. Other affected nodes in the network use the TPC of the STP to direct related network status queries to that STP. Because conventional STPs only have a single true point code, each STP is only capable of serving a single network. Stated differently, at least one STP per network is required for network management purposes.
There are a number of routing management messages commonly employed to re-direct traffic around a failed or congested route. Such messages may be sent by an SS7 signaling point in response to the failure of one or more provisioned links. More particularly, when a route fails, a routing management message is sent to all neighboring SS7 signaling nodes (i.e., those SS7 signaling nodes that are adjacent to the troubled signaling node). This routing management message informs the neighboring SS7 signaling nodes of the problem at the troubled node and also provides instructions regarding future routing to the troubled node. Routing management messages are also used to inform neighboring SS7 signaling nodes of the recovery of a previously troubled node. SS7 routing management messages include: transfer prohibited (TFP), transfer restricted (TFR), transfer controlled (TFC), transfer allowed (TFA) messages, transfer cluster prohibited (TCP), and transfer cluster allowed (TCA). These messages are only a subset of all network management messages defined in the SS7 protocol.
A transfer prohibited message is generated and transmitted by an SS7 signaling point (e.g., an STP) in response to determining that communication with an SS7 node is no longer possible. A transfer restricted message may be sent in response to determining that communication with an SS7 node is possible, but sub-optimal. A TFR message requests that adjacent SS7 signaling points use alternate routes when sending messages to the troubled SS7 node. If alternate routes are not available, messages may continue to be routed normally. A transfer controlled message is sent by an SS7 signaling point (e.g., an STP) in response to the receipt of an MSU destined for a congested route. In such a scenario, the MSU is discarded, and a TFC message is returned to the originator or sender of the MSU. A transfer allowed message is sent by an SS7 signaling point when a previously failed route becomes available.
Referring back to FIG. 1, each network includes a single STP. It may be desirable to reduce the number of STPs for cost, reliability, or regulatory reasons. However, as stated above, conventional STPs are only capable of performing network management using a single true point code. Thus, replacing multiple STPs with a single STP would require re-provisioning of network nodes to communicate with the new STP. Reprovisioning all nodes in a network to communicate with a new STP is undesirable because of the time and labor involved in reprogramming each individual node. Accordingly, there exists a long-felt need for methods and systems for seamlessly reducing the number of STPs in a signaling network.
The present invention includes a multiple point code routing node that assumes more than one true point code for SS7 routing and network management message origination and termination. STPs have conventionally had only one true point code. The present invention introduces the concept of a secondary true point code, which allows a routing node, such as an STP, to function as if it has more than one true point code. A secondary true point code is different from a conventional capability point code in that true point codes are used for network management messages; whereas capability point codes are used for SCCP messages.
According to one aspect, the present invention includes a routing node provisioned to respond to a true point code and a secondary true point code. The secondary true point code may correspond to the true point code of an STP being replaced by the routing node. Because a routing node can be provisioned to respond to both a true point code and one or more secondary true point codes, the signaling network infrastructure can be simplified without reconfiguring network elements to communicate with a new routing node having a new true point code.
According to another aspect, the present invention includes a method for originating network management messages from a multiple point code routing node. When a multiple point code routing node receives notification of a network management event, such as a signaling link failure, the multiple point code routing node originates network management messages to other networks. When formulating a network management message, the multiple point code routing node inserts its true point code or one of its secondary true point codes in the OPC field of a network management message, depending on the destination network. When sending messages to a mated routing node, the multiple point code routing node must select the correct DPC to include in the network management message. For example, if a mated routing node has two true point codes, the multiple point code routing node originating a network management message chooses between the true point codes depending on the replaced STP that would have originally received the message. Finally, the multiple point code routing node may include a concerned point code in the network management message to indicate the failed signaling link. Because the multiple point code routing node is capable of using multiple true point codes in network management messages that it originates, the network management functionality of multiple STPs can be seamlessly replaced.
In addition to the secondary point code addressing scheme discussed above, a mated pair of MPC routing nodes of the present invention may recognize multiple adjacent point codes in order to facilitate the reliable communication of signaling messages (e.g., network management messages, call setup/teardown messages, query messages, etc. ) between mates. An adjacent point code is the point code of a node at the remote end of an SS7 signaling link. For example, STPs of a mated pair may be connected by C links. In conventional SS7 networks, the adjacent point code recognized by each STP in a mated pair of STPs was set to the single true point code of its mate. Setting the adjacent point code to the true point code of a mate STP allows each STP to reroute traffic through its mate STP in the event of a signaling link failure. STPs according to the present invention can be provisioned to respond to multiple true point codes and to associate multiple adjacent point codes with their mates. Because each STP of a mated pair can associate multiple adjacent point codes with its mate, multiple C linksets can be used to interconnect the STPs. As a result, reliability of the pair is increased.
In an alternate implementation, each STP of a mated pair may be connected by one or more IP signaling links. In such an implementation, each STP may associate multiple adjacent point codes with its mate over the IP signaling link. Thus, a single IP link may function as multiple SS7 C linksets by using multiple adjacent point codes. The ability to function as multiple logical C links over an IP link provides increased reliability without the need for adding new SS7 C linksets.
The functions for providing multiple point code routing support are described herein as modules, applications, or processes. It is understood that these modules, applications, or processes may be implemented as computer-executable instructions embodied in a computer-readable medium. Alternatively, the modules, applications, or processes described herein may be implemented entirely in hardware. In yet another alternative embodiment, the modules, applications, or processes described herein may be implemented as a combination of hardware and software.
The modules, applications, and processes for providing multiple point code routing functionality are described below as being associated with cards or subsystems within an STP or signaling gateway routing node. It is understood that these cards or subsystems include hardware for storing and executing the processes and modules. For example, each card or subsystems described below may include one or more microprocessors, such as an x86 microprocessor available from Intel Corporation or a K-series microprocessor available from AMD Corporation, and associated memory.
Accordingly, it is an object of the present invention to provide a routing node that assumes the true point code identities of other signal transfer point routing nodes in one or more SS7 signaling networks.
It is another object of the present invention to provide a routing node that replaces one or more STPs by assuming their true point code identities.
It is another object of the present invention to provide a system and method of collapsing or reducing STP infrastructure requirements in a signaling network environment while minimally impacting other signaling points in the signaling network environment.
It is another object of the present invention to provide a system and method for enabling multiple SS7 signaling links and linksets to be provisioned between a mated pair of STPs.
It is yet another object of the present invention to provide a routing node for maintaining SS7 network management integrity while assuming multiple true point code identities.
It is yet another object of the present invention to provide a routing node that functions as a plurality of virtual STPs, where each virtual STP communicates with adjacent nodes using a different true point code.
It is yet another object of the present invention to provide a mated pair of routing nodes that communicate with one another using a plurality of different adjacent point codes.
It is yet another object of the invention to provide an STP capable of serving multiple networks.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow.